Anyway, I went to their house this weekend, they were getting ready to their US trip when I saw their tank, I didn't know they had a fish until then (neither they knew about me with my tropical fishes... lol).

Anyhow, their tank is with an extreme poor water quality in it, they didn't even know when was the last water change, the original filter doesn't work and the other filter they have on it they never actually keep it on;

I said I could take them home so I could try to take care about them but they said was way too last minute and their other neighbour would take care of them instead (only feeding them once every 2 days)...

I'm pretty sure the 2nd one will die in the end of this week before they return.. Buuuut in case it doesn't, they said they will bring the fishes here for me to take care of them;

Also, it bothers me they have everything on their house and they never used it... >_>! Not even water conditioner... Poor fishies, I can't do anything but wait for the week to pass but idk ;V it is bothering me a lot.

So, my question is:

- Can I do the same treatment I would to for the same illnesses on a betta for a goldfish? Cus I know they are cold water fish rather than tropical ones.

I don't know all that much, but clean water will begin to do wonders for their health, along with a proper sized tank. 20 gallons per fish. you could contact Lupin, he's pretty much a goldfish expert on here.

I always though common goldfish needed 50 gallons each? So two common goldfish need a 100 gallon tank?
Unless they're fancy goldfish, which need 20 gallons for the first fish and an additional 10 gallons for every other fish. So two fancy goldfish need a 30 gallon tank?

I'm afraid asking for them to buy a bigger tank is out of the question. >_>

I'm more concerned about salt/medicine dosage in a way, although I do know about the proper size and stuff, they just... They won't buy a bigger tank, they only have a tank "that big" because a friend of them gave it to them.

So I'm more like, giving to them more or less a routine of how to keep them healthy after treating them. Such as when to do the water changes, the conditioner and stuff.. I know you should only have a fish when you can give it a proper care, actually this goes to any animals but still =/

They will stay "small" on the outside in a small tank, but there organs grow, and eventually become too big for their bodies, and are all smushed together, which causes them to die prematurely.

There is the "mother" of bettafish.com, which is tropicalfiskeeping.com, where you can ask more people who know about goldfish more in-depth treatment questions. Your login here can be used to login at tropicalfishkeeping.com. There are a lot of really nice, informative people there. :)

Good luck. I can understand how difficult it would be to convince them to get a bigger tank. I hate how its become "common knowledge" that a goldfish can live in small spaces, its cruel.

Maybe direct them to a site that clearly states they need bigger tanks, as well as other info, and then be like "huh, I had NO IDEA that goldfish needed such big tanks! I completely missed the section on THAT." XD

Anyhoo, good luck treating them, if and (hopefully) when, you treat them.